Transmission transducer for remote measurement

ABSTRACT

A transmission transducer for remote measurement is incorporated in the feedback loop of a double integrator type oscillator. The transducer is adapted to control the frequency of the oscillator corresponding to variations of gains of the transducer. The transducer gain is varied in accordance with variations of measured values which are directly sensed by the transducer.

United States Patent [72] Inventors EtsujiroShimemura Tokyo; Masaolwamiya, Yokohama-511i, both of, Japan [211 App]. No. 763,782

[22] Filed Sept. 30, 1968 [45] Patented May 25, 1971 [73] Assignee TheTsurumi-Seikikosakv-Sho Co. LTD Yokohama-shi, Japan [32] Priority Sept.30, 1967 [33] Japan [31] 62756/1967 [54] TRANSMISSION TRANSDUCER FORREMOTE MEASUREMENT 7 Claims, 6 Drawing Figs.

[52] US. Cl 331/135, 331/136 [5 l] Int. Cl 1103b 5/20 n 13,5s1,23s

[50] Field ofSearch 331/135, 136

[56] References Cited UNITED STATES PATENTS 3,396,346 8/l 968 Richman331/135 OTHER REFERENCES E. F. Good, Electronic Engineering Pgs. 164-169 April 1957, 331135 Primary Examiner-John Kominski Attorney-Flynn andFrishauf ABSTRACT: A transmission transducer for remote measurement isincorporated in the feedback loop of a double integrator typeoscillator. The transducer is adapted to control the frequency of theoscillator corresponding to variations of gains of the transducer. Thetransducer gain is varied in accordance with variations of measuredvalues which are directly sensed by the transducer.

TRANSMISSION TRANSDUCER FOR REMOTE MEASUREMENT BACKGROUND OF THEINVENTION The present invention relates to a transmission transducer forremote measurement and more particularly to improve ments in anoscillator-type transmission transducer.

Among the methods of telemetering the data, there is one known as the FMsystem. This system further includes, for example, (a) a voltagecontrolled type oscillator, (b) a balanced torque type voltagecontrolled oscillator and (c) a resistance controlled oscillator.

There will now be described an oscillator-type transmission transducer.To measure values such as those associated with temperature, salinity ofsea water, ocean depth, direction and velocity of ocean currents andsound velocity in the water, there is used a primary transducer, forexample, a thermistor, an inductive conductivity head, a potentiometerto detect variations in pressure using a bourdon tube or a potentiometerto detect current direction from the rotation angle of a vane. Measuredvalues are proportionally converted to a direct cur rent voltage, whichin turn is proportionally converted to a frequency by a secondarytransducer, for example, an oscillator, thereby to transmit the measuredvalues.

The aforementioned oscillator must have its frequency controlled inaccordance with variations in the range of measured values. To this end,there had been employed a phase control system using a Wien-bridgecircuit or a voltage or current control system using a multivibrator.

However, these frequency control systems involved unstable factors suchas a direct current amplifier which was subject to severe drifting.Therefore, when they were used in a locality where it was impossible toexpect stable environmental conditions, they were unavoidably reduced inthe accuracy of measurement as was the case with an ocean telemeter.

The conventional frequency control method was incapable of separatelycarrying out the adjustment of the center frequency corresponding to thestandard measured values and the occupied frequency bandwidthcorresponding to variations in the range of measured values. Forinstance, if it is assumed that outputs from the primary transducercorresponding to variations in the range of measured values have avoltage ranging between E V and E,V and that frequencies from theoscillator corresponding to the aforesaid range of voltage extend from fels to f cls, then the voltage of outputs from the primary transducerwill be broadened from E V to E V, provided to upper limit of the rangeof measurement is enlarged. However, due to the intrinsic properties ofthe oscillator itself, if the upper limit E,V of the voltage range waschanged to E V, this also varied the center frequency f els and thelower limit of the range of the corresponding frequencies, making itimpossible to easily obtain an occupied frequency bandwidth of from fels to f c/s exactly corresponding to the enlargement of the aforesaidvoltage range. To overcome these drawbacks, there has been adopted, forexample, a method which consisted in first setting the lower limitvoltage E V at v. using the balancing conditions of a bridge circuit,and thereafter changing the upper limit voltage E,V to E V. However,this method involved a complicated and expensive apparatus and there hasbeen voiced a strong demand for its improvement.

SUMMARY OF THE INVENTION The present invention provides a transmissiontransducer for remote measurement, which is incorporated in the loop ofa double integrator type oscillator, and which is adapted to control thefrequency of the oscillator. Variations of measured values are directlysensed by the transducer, and are directly converted to variations ingain of the transducer. The transducer is coupled in the feedbackoscillator circuit so that variations in gain thereof causecorrespondingly variations in oscillator frequency. The transducersystem can be easily constructed and operated reliably even whereenvironmental conditions change and moreover can control the centerfrequency LII and occupied frequency bandwidth independently of eachother, affording the advantage of improving the accuracy of measurementand other merits.

BRIEF EXPLANATION OF THE DRAWINGS FIGS. 1, 2 and 3 are block diagramsillustrative of the principle of the present invention;

FIG. 4 is a block diagram schematically showing the construction of anapparatus according to the present invention;

FIG. 5 represents the concrete circuit pattern of the present invention;and

FIG. 6 represents an amplitude stabilizing circuit.

DETAILED DESCRIPTION OF THE INVENTION As shown in FIG. 1, thetransmission transducer assembly of the present invention consists of atransducer I and oscillator II. To one input terminal t of thetransducer I are supplied measured values, which are then conducted tothe input terminal t of the oscillator II. The output terminal of theoscillator II is connected to the other input terminal of the transducerI so as to form a closed loop oscillation circuit including saidtransducer I.

As is well known, a system represented by the following differentialequation of the second order W w 6 0 l performs simple harmonic motionof an angular frequency m. If represented by a clock circuit diagram asshown in FIG. 2, the system which performs simple harmonic motionexpressed by the above equation (1) consists of a double integrator DIdesignated as (j dt) and a coefficient adjuster C for feeding backoutputs therefrom. With the feedback gain of the coefficient adjusterdenoted as B, the angular frequency w in the block circuit diagram maybe expressed as follows:

Now let it be assumed that as shown in FIG. 3, the coeffi cient adjusterC of FIG. 2 consists of three component units C C and C and that thegains of these units are designated as AB, 11. and B respectively. Ifthe three coefficient adjuster units C C and C of FIG. 3 areincorporated into the coefficient adjuster C of FIG. 2, the resultantcircuit will assume a pattern as shown in FIG. 4. The overall gain [3 ofthe coefficient adjuster C will be B=BO+ILAB and the angular frequency wthereof will be w fio B JED 0 If B then equation (4) may beapproximately expressed as follows by rearranging the equation byTaylor's development to omit the second and subsequent terms.

I Afi N/Boi m The frequency f of signals from the oscillator II and thegains of the respective coefficient adjuster units C C and C forming theexternal circuit 0 the oscillator II have a relationship:

1 f= N I 0+M I (6) The relationship of frequency to gain is such thatthe center frequency f representing the standard measured values isdetermined in accordance with the gain B of the coefficient adjusterunit C and that the gain defining the upper limit frequency f beyond thecenter frequency f,,, namely, the occupied frequency bandwidth, is fixedin accordance with the product A3 of the gains p. and AB of the othercoefficient adjuster units C and C,, respectively.

Since the first term of equation corresponds to the center frequency,and the second term to the occupied frequency bandwidth, the centerfrequency may be freely set by adjusting the gain [3 of the coefficientadjuster unit C and the occupied frequency bandwidth by adjusting thegain p. of the coefficient adjuster unit C Moreover, the presentinvention enables these adjustments to be carried out separately.

There will now be described the concrete block circuit diagram of FIG. 4by reference to FIG. 5. To the input terminal I, of the primarytransducer 11 are supplied measured amounts (or values) M. Outputs efrom the primary transducer are conducted to the circuit 12 foradjusting the occupied frequency bandwidth. The adjusting circuit 12consists of a serial circuit comprising a resistor r and an operationalamplifier A and a resistor r connected between the output and inputterminals of the operational amplifier A to form a feedback circuit.Outputs from the circuit 12 for adjusting the occupied frequencybandwidth are supplied to the input terminal of the double integrator13. This double integrator 13 comprises a first integrating circuitwherein a resistor r and operational amplifier A are connected inseries, and a condenser C is connected between the output and inputterminals of the operational amplifier A to form an integrating circuittogether with the resistor r and also a second integrating circuit whichis serially connected to the first integrating circuit and includes aresistor r operational amplifier A 3 and condenser C Outputs from thedouble integrating circuit 13 are fed back to the center frequencyadjusting circuit 14 and primary transducer 11. The center frequencyadjusting circuit 14 consists of a variable resistor grounded at oneend, the movable contact of which is connected through a resistor r tothe other input terminal of the operational amplifier A At the outputterminal of the operational amplifier A is positioned an actuatingcircuit 15 comprising a variable resistor grounded at one end. Themovable contact of the variable resistor is connected through a resistorr to the input terminal of the operational amplifier A One end of thecondenser C is connected to the connection point of the resistor r andoperational amplifier A, and the other end of the condenser C isgrounded.

To both ends of the condenser C of the second integrating circuit isconnected an amplitude stabilizing circuit 16. This amplitudestabilizing circuit 16 consists of, for example, a bridge circuit asshown in FIG. 6 wherein the group of diode D, and resistor r, and thegroup of diode D and resistor r are respectively positioned on eitherside of the bridge and these groups are connected through the respectiveresistors r and r, to the respective terminals 0 and b of a source ofdirect current, and the output terminal of the bridge circuit isconnected to the condenser C of the second integrating circuit.

The gain AB of the primary transducer 11 is determined by the ratio ofthe output e from said transducer 11 to the signal e, issued from theoscillator, and can be controlled in accordance with the measuredvalves.

On the other hand, the gain [3 corresponding to the center frequency fcan be defined by sliding to any desired position the movable contact ofthe variable resistor constituting the circuit for adjusting the centerfrequency and supplying the resultant output to the first integrator ofthe oscillator. Therefore the gain of the entire apparatus is determinedjointly by the gain [3 fixed by the oscillator itself, the gain AB ofthe primary transducer l provided in the external circuit of theoscillator and the gain p. of the other circuit including an operationalamplifier, so that the upper limit of the occupied frequency bandwidthcan be controlled by the external circuit of the oscillator (i.e., byadjusting the gain a of circuit 12) independently of the centerfrequency.

he actuating circuit 15 is intended to cause oscillation to be easilystarted, and the amplitude stabilizing circuit 16 is used in controllingincreases in the amplitude of the output from the second integratingcircuit.

The aforementioned circuit arrangement of the present invention canindependently control the center frequency and occupied frequencybandwidth, which are defined by the measured amounts, without any effecton either of these factors. This eliminates the necessity of using acomplicated circuit system such as the conventional type, renders theentire apparatus compact and of lightweight and permits easy replacementof the parts thereof. Due to the aforementioned merits, the apparatus ofthe present invention is well adapted for use in telemeters to indicateocean conditions, weather conditions, and outer space conditions so asto help the progress in these studies.

What we claim is:

1. A feedback-type oscillator apparatus for remote measurementcomprising:

a variable gain transducer, the gain of which is variable in accordancewith inputs thereto which correspond to values which are to be remotelymeasured;

a first coefficient adjuster coupled to an output of said variable gaintransducer and adapted to adjust the occupied frequency bandwidth of themeasurement apparatus;

a double integrator coupled to the output of said first coefficientadjuster, said double integrator including serially connected first andsecond integrator units;

a second coefficient adjuster coupling an output of said doubleintegrator to an input of said first integrator unit, said secondcoefficient adjuster adjusting the center frequency of the measurementapparatus independent of the occupied frequency bandwidth; and

a feedback circuit for feeding back an output signal of said doubleintegrator to said variable gain transducer for stabilizing thevariations of gain of said variable gain transducer produced by thevariations of said values being remotely measured.

2. Apparatus according to claim 1 wherein said first coefficientadjuster includes a series circuit which comprises a resistor coupled tothe output of said variable gain transducer connected in series with anoperational amplifier, the output of the operational amplifier beingcoupled to said double integrator. I

3. Apparatus according to claim 1 wherein each of said integrator unitsincluded in said double integrator comprises an operational amplifier, aresistor series connected thereto, and a condenser connected in parallelwith the respective operational amplifier.

4. Apparatus according to claim 1 wherein said second coefiicientadjuster includes a variable resistor coupling an output from saiddouble integrator to an input terminal of said first integrator unit.

5. Apparatus according to claim 2 wherein said second coefficientadjuster includes a variable resistor coupling an output from saiddouble integrator to an input terminal of said first integrator unit.

6. Apparatus according to claim 3 wherein said second coefficientadjuster includes a variable resistor coupling an output from saiddouble integrator to an input terminal of the operational amplifier ofsaid first integrator unit.

7. Apparatus according to claim 3 further comprising: an actuatingcircuit for facilitating initial oscillation, said actuating circuitincluding a variable resistor coupled between the output and inputterminals of the operational amplifier of said first integrator unit;and an amplitude stabilizing circuit coupled between the terminals ofthe condenser of said second in tegrator unit.

1. A feedback-type oscillator apparatus for remote measurementcomprising: a variable gain transducer, the gain of which is variable inaccordance with inputs thereto which correspond to values which are tobe remotely measured; a first coefficient adjuster coupled to an outputof said variable gain transducer and adapted to adjust the occupiedfrequency bandwidth of the measurement apparatus; a double integratorcoupled to the output of said first coefficient adjuster, said doubleintegrator including serially connected first and second integratorunits; a second coefficient adjuster coupling an output of said doubleintegrator to an input of said first integrator unit, said secondcoefficient adjuster adjusting the center frequency of the measurementapparatus independent of the occupied frequency bandwidth; and afeedback circuit for feeding back an output signal of said doubleintegrator to said variable gain transducer for stabilizing thevariations of gain of said variable gain transducer produced by thevariations of said values being remotely measured.
 2. Apparatusaccording to claim 1 wherein said first coefficient adjuster includes aseries circuit which comprises a resistor coupled to the output of saidvariable gain transducer connected in series with an operationalamplifier, the output of the operational amplifier being coupled to saiddouble integrator.
 3. Apparatus according to claim 1 wherein each ofsaid integrator units included in said double integrator comprises anoperational amplifier, a resistor series connected thereto, and acondenser connected in parallel with the respective operationalamplifier.
 4. Apparatus according to claim 1 wherein said secondcoefficient adjuster includes a variable resistor coupling an outputfrom said double integrator to an input terminal of said firstintegrator unit.
 5. Apparatus according to claim 2 wherein said secondcoefficient adjuster includes a variable resistor coupling an outputfrom said double integrator to an inPut terminal of said firstintegrator unit.
 6. Apparatus according to claim 3 wherein said secondcoefficient adjuster includes a variable resistor coupling an outputfrom said double integrator to an input terminal of the operationalamplifier of said first integrator unit.
 7. Apparatus according to claim3 further comprising: an actuating circuit for facilitating initialoscillation, said actuating circuit including a variable resistorcoupled between the output and input terminals of the operationalamplifier of said first integrator unit; and an amplitude stabilizingcircuit coupled between the terminals of the condenser of said secondintegrator unit.